Operating Systems for Reconfigurable Embedded Platforms Online Scheduling
Operating Systems for Reconfigurable Embedded Platforms: Online Scheduling of Real-Time Tasks -Ramkumar Shankar
Reference C. Steiger, H. Walder and M. Platzner, “Operating Systems for Reconfigurable Embedded Platforms: Online Scheduling of Real-Time Tasks” , IEEE Transactions on computers vol 53, No. 11, pp. 1393 -1407 Nov. 2004 Web link: http: //ieeexplore. ieee. org/xpls/abs_all. jsp? arnumber= 1336761 2
Outline Models and Limitations Practical OS Target Architecture OS Modules Scheduling Real-Time Tasks Techniques for 1 D and 2 D model Results, Conclusion and Future Scope 3
Preliminaries Hardware task Digital circuit that has been preplaced and prerouted. Functional characteristics transparent to the OS. Structural characteristics visible to the OS. 4 Area and timing requirements
1 D and 2 D area model 5
Limitations of the area model Internal Fragmentation External Fragmentation Assumes Homogeneity of the RC Device. 6 OS takes up some of the special resources Tasks not relocatable
Target Architecture 7
Partitioning of the RC device 8
Operating system modules 9
Operating System Modules on CPU Task Scheduler Resource Manager Task Preparation Unit Raw Task Repository COMM Driver C/R Driver 10
Operating System Modules on RC Device Task Controller Memory Management Unit(MMU) Device Drivers OS Bridge 11
Scheduling Real-Time Tasks Factors affecting the scheduling: arrival time, execution time, deadline Width, height Constraints for the scheduler 12 Scheduled tasks must not overlap in space and time The tasks must meet the deadline
1 D Horizon Technique Execution list (E) Reservation List (R) Maintains tasks (Ti), Finish time(fi) and placement(xi) Stores all tasks scheduled but not executing Horizon List(H) 13 Stores the position and time step at which the units become available.
1 D Horizon Technique example 14
1 D Stuffing Technique Maintains Execution and Reservation lists Maintains a free space list. 15
Placement Algorithms and related issues Free space management Merging free spaces in Horizon Technique. Mimic future tasks for Stuffing Technique. Strip Packing Scheduling tasks for 2 D mesh – very costly 16
Evaluation 17
Results 18
Conclusion and Further Work Design issues for RC Hardware operating system. Scheduling techniques for 1 D and 2 D area models Scheduling tasks for non-real time systems Tasks with unknown execution times Tasks without deadlines Periodic tasks 19
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Questions 21
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